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This invention relates to digital packet telecommunications, and particularly to management of network bandwidth based on information ascertainable from multiple layers of OSI network model. It is particularly useful in conjunction with bandwidth allocation mechanisms employing traffic classification in a digitally-switched packet telecommunications environment, as well as in monitoriing, security and routing.
The ubiquitous TCP/IP protocol suite, which implements the world-wide data communication network environment called the Internet and is also used in private networks (Intranets), intentionally omits explicit supervisory function over the rate of data transport over the various media which comprise the network. While there are certain perceived advantages, this characteristic has the consequence of juxtaposing very high-speed packet flows and very low-speed packet flows in potential conflict for network resources, which results in inefficiencies. Certain pathological loading conditions can result in instability, overloading and data transfer stoppage. Therefore, it is desirable to provide some mechanism to optimize efficiency of data transfer while minimizing the risk of data loss. Early indication of the rate of data flow which can or must be supported is imperative. In fact, data flow rate capacity information is a key factor for use in resource allocation decisions. For example, if a particular path is inadequate to accommodate a high rate of data flow, an alternative route can be sought out.
Internet/Intranet technology is based largely on the TCP/IP protocol suite, where IP, or Internet Protocol, is the network layer protocol and TCP, or Transmission Control Protocol, is the transport layer protocol. At the network level, IP provides a xe2x80x9cdatagramxe2x80x9d delivery service. By contrast, TCP builds a transport level service over the datagram service to provide guaranteed, sequential delivery of a byte stream between two IP hosts.
TCP flow control mechanisms operate exclusively at the end stations to limit the rate at which TCP endpoints emit data. However, TCP lacks explicit data rate control. The basic flow control mechanism is a sliding window, superimposed on a range of bytes beyond the last explicitly-acknowledged byte. Its sliding operation limits the amount of unacknowledged transmissible data that a TCP endpoint can emit.
Another flow control mechanism is a congestion window, which is a refinement of the sliding window scheme, which employs conservative expansion to fully utilize all of the allowable window. A component of this mechanism is sometimes referred to as xe2x80x9cslow startxe2x80x9d.
The sliding window flow control mechanism works in conjunction with the Retransmit Timeout Mechanism (RTO), which is a timeout to prompt a retransmission of unacknowledged data. The timeout length is based on a running average of the Round Trip Time (RTT) for acknowledgment receipt, i.e. if an acknowledgment is not received within (typically) the smoothed RTT+4*mean deviation, then packet loss is inferred and the data pending acknowledgment is retransmitted.
Data rate flow control mechanisms which are operative end-to-end without explicit data rate control draw a strong inference of congestion from packet loss (inferred, typically, by RTO). TCP end systems, for example, will xe2x80x98back-offxe2x80x99, i.e., inhibit transmission in increasing multiples of the base RTT average as a reaction to consecutive packet loss.
Bandwidth Management in TCP/IP Networks
Conventional bandwidth management in TCP/IP networks is accomplished by a combination of TCP end systems and routers which queue packets and discard packets when certain congestion thresholds are exceeded. The discarded, and therefore unacknowledged, packet serves as a feedback mechanism to the TCP transmitter. (TCP end systems are clients or servers running the TCP transport protocol, typically as part of their operating system.)
The term xe2x80x9cbandwidth managementxe2x80x9d is often used to refer to link level bandwidth management, e.g. multiple line support for Point to Point Protocol (PPP). Link level bandwidth management is essentially the process of keeping track of all traffic and deciding whether an additional dial line or ISDN channel should be opened or an extraneous one closed. The field of this invention is concerned with network level bandwidth management, i.e. policies to assign available bandwidth from a single logical link to network flows.
In a copending U.S. patent application Ser. No. 08/742,994, now U.S. Pat. No. 6,038,216, in the name of Robert L. Packer, entitled xe2x80x9cMethod for Explicit Data Rate Control in a Packet Communication Environment Without Data Rate Supervision,xe2x80x9d a technique for automatically scheduling TCP packets for transmission is disclosed. Furthermore, in U.S. Pat. No. 5,802,106, in the name of Robert L. Packer, entitled xe2x80x9cMethod for Rapid Data Rate Detection in a Packet Communication Environment Without Data Rate Supervision,xe2x80x9d a technique for automatically determining the data rate of a TCP connection is disclosed. Finally, in a copending U.S. patent application Ser. No. 08/977,376, now abandoned in the name of Robert L. Packer, entitled xe2x80x9cMethod for Managing Flow Bandwidth Utilization at Network, Transport and Application Layers in Store and Forward Network,xe2x80x9d a technique for automatically allocating bandwidth based upon data rates of TCP connections according to a hierarchical classification paradigm is disclosed.
Automated tools assist the network manager in configuring and managing the network equipped with the rate control techniques described in these copending applications. In a related copending application, a tool is described which enables a network manager to automatically produce policies for traffic being automatically detected in a network. It is described in a copending U.S. patent application Ser. No. 09/198,051, still pending, in the name of Guy Riddle, entitled xe2x80x9cMethod for Automatically Determining a Traffic Policy in a Packet Communications Networkxe2x80x9d, based on U.S. Provisional Patent Application Serial No. 60/066,864. The subject of the present invention is also a tool designed to assist the network manager.
While these efforts teach methods for solving problems associated with scheduling transmissions, automatically determining data flow rate on a TCP connection, allocating bandwidth based upon a classification of network traffic and automatically determining a policy, respectively, there is no teaching in the prior art of methods for automatically classifying packet traffic based upon information gathered from a multiple layers in a multi-layer protocol network.
Bandwidth has become the expensive commodity of the ""90s, as traffic expands faster than resources, the need to xe2x80x9cprioritizexe2x80x9d a scarce resource, becomes ever more critical. One way to solve this is by applying xe2x80x9cpoliciesxe2x80x9d to control traffic classified as to type of service required in order to more efficiently match resources with traffic.
Traffic may be classified by type, e.g. E-mail, web surfing, file transfer, at various levels. For example, to classify by network paradigm, examining messages for an IEEE source/destination service access point (SAP) or a sub-layer access protocol (SNAP) yields a very broad indicator, i.e., SNA or IP. More specific types exist, such as whether an IP protocol field in an IP header indicates TCP or UDP. Well known connection ports provide indications at the application layer, i.e., SMTP or HTTP.
Classification is not new. Firewall products like xe2x80x9cCheckPoint FireWall-1,xe2x80x9d a product of CheckPoint Software Technologies, Inc., a company with headquarters in Redwood City, Calif., have rules for matching traffic. Bandwidth managers such as xe2x80x9cAponet,xe2x80x9d a product of Aponet, Inc., a company with headquarters in San Jose, Calif., classify by destination. The PacketShaper, a product of Packeteer, Inc., a company with headquarters in Cupertino, Calif., allows a user to manually enter rules to match various traffic types for statistical tracking, i.e., counting by transaction, byte count, rates, etc. However, manual rule entry requires a level of expertise that limits the appeal for such a system to network savvy customers. What is really needed is a method for analyzing real traffic in a customer""s network and automatically producing a list of the xe2x80x9cfound traffic.xe2x80x9d
According to the invention, in a packet communication environment, a method is provided for automatically classifying packet flows for use in allocating bandwidth resources and the like by a rule of assignment of a service level. The method comprises applying individual instances of traffic classification paradigms to packet network flows based on selectable information obtained from a plurality of layers of a multi-layered communication protocol in order to define a characteristic class, then mapping the flow to the defined traffic class. It is useful to note that the automatic classification is sufficiently robust to classify a complete enumeration of the possible traffic.
In the present invention network managers need not know the technical aspects of each kind of traffic in order to configure traffic classes and service aggregates bundle traffic to provide a convenience to the user, by clarifying processing and enables the user to obtain group counts of all parts comprising a service.
The invention will be better understood upon reference to the following detailed description in connection with the accompanying drawings.